DF225 Running Rich and Making Oil

[Makeitdo22]

I’m hoping this community can help resolve another “making oil” engine. I’ve scoured multiple forums and found a lot of good information, but I have yet to find the smoking gun to resolve my issue.

I have a 2015 DF225 that is making oil at a rate of about 1 to 1.5 quarts per 50 hours of operation. An oil analysis confirmed that it is fuel in the oil (3.9% fuel dilution after 80 hours of operation). Current hours are 274. I do minimal idling and trolling. Typically run between 4,200-4,500 rpm. PowerTech OSF4 Prop, 4 blade, 19” pitch, WOT with a full tank and 2 people is 5950 rpm. The boat has plenty of power, with a top end around 42 mph. Idle is 656 rpm. The engine is running rich. I can smell the fuel in the exhaust and there is a lot of black residue on the mid-section each time I operate the boat.

My best guess is that these symptoms started 2.5 years ago when the dealer failed to put the water pump sleeve in my lower unit, which caused my engine to overheat and shutdown - fortunately, I was in the marina when this occurred. So much for going to the dealership for maintenance to keep a warranty. Unfortunately for me, my warranty ran out by the time I realized that I had an issue making oil. So needless to say, I’m back to doing my own engine work here in Panama City, Florida. Prior to this event, I was able to achieve 2.8 mpg. The best that I can do now is 2.3 mpg (no bottom paint or other drag components have been added).

Troubleshooting completed to date:
Cleaned all battery terminals and checked voltage at the engine (12.76V)
Tested Thermostats to confirm 140 degree F open prior to installation. Engine runs at 140 F at idle. I observe 160s when underway around 4,500 rpm.
Replaced water pressure valve
Compression check satisfactory (Sat): all cylinders 210 psi +- 5 psi
Fuel System pressure check Sat: 35.9 psi while running (spec is 36.3 psi). Seems to be with the error of my gauge.
Fuel System residual pressure check after 5 mins Sat: 30.4 psi (spec is 28.4 psi)
Vacuum Test performed and is Sat: 20.5 inHg (spec is 18-21 inHg)
Removed Fuel Injectors and sent them off for analysis and reconditioning. Testing came back all Sat with fuel injector spray pattern and no leaky injectors (as evident from the earlier fuel residual pressure check).
Monitored the following sensors using SDS and verified they were operating within spec: Throttle Position Sensor, Manifold Air Pressure (MAP), Intake Air temperature

Next Steps:

• Use a thermal gun to verify both sides thermostats are functioning properly (be sure that one is not stuck open).
• Perform the O2 Feedback Procedure to hopefully reset the Air to Fuel ratio table. Need help identifying the correct wiring harness part number and O2 Sensor install location (not shown in the manual).
• ? - Open to suggestions

Is there another path for fuel to get into the oil that I am missing? I do not have the evaporator purge system on this engine and I cannot find any direct path for fuel to make it’s way into the crankcase other than through the injectors.

Thanks in advance for the help.

[redlowrey]

What do you mean there is no evap system, how does it vent the vst.
The problem must be obvious if you can smell it is running rich, and there is soot on the mid section.
The fuel trims from the O2 sensor would indicate it was removing fuel to keep the air fuel ratio right.

[Makeitdo22]

Good question. I meant to say that there is no purge valve in the evap system, but there is a vent tube that runs to outside of the engine.

Are you saying that I should check the fuel trim data through the SDS (I'm running version 8.5)? Or are you suggesting to perform the O2 Feedback procedure to enable the system to update the fuel trims?

The manual calls for using O2 Sensor 18213-74F00 and a protector 18498-99E70. I have both of these, but I cannot find where to hook the O2 sensor into the wiring harness or where the O2 Sensor is installed onto the engine. Since the manual that I have isn't very clear, I am assuming that the diagnostic harness 09932-79910 and the SDS adapter 09932-89910 are used to plug into the ECU, the computer running SDS, and the O2 sensor at the same time. Is this right equipment needed to perform the O2 Feedback procedure? Does anyone have a picture of where the O2 Sensor is threaded into the engine?

[redlowrey]

I need to know where that vent line connects into the system, surely it does not vent into the crankcase.

Don’t worry about the 02 sensor at the moment, find out where that vent line is going first.

[Makeitdo22]

3BEB3BC4-FD3A-4F8E-B4FB-BF1D32579802.jpeg This picture shows the VST vent tube exit to atmosphere. It runs from the VST to above the engine on the port side before turning downward and exiting the engine behind/below the VST. In this instance it is not entering the crankcase.

[redlowrey]

I can’t believe that hose can vent to atmosphere, can you put up some history showing some sds data with the engine running at operating temp.
I want to see what your map sensor signal voltage is at idle and any other rpm.
Also inlet air temp and engine temp signal voltages hot and cold.

Can you pull the hose off the vst and blow through the other end and see if air blows out, and look at the fitting coming out of the vst and see how big the opening is. Something does not add up.

Pull a couple of plugs out and look at the colour of the porcelain near the electrode, eg, black, tan, or white.
That will give me some information of what is going on in the combustion chamber.

[Makeitdo22]

fullsizeoutput_11202.jpegIMG_2567.jpg
Here are the spark plugs when I changed them in August. Port side is in the first picture #2,4,6 cylinders from top down. Starboard side is in the second pic #1,3,5 from top down. I noted that #2,4 & 3 appeared wet. I'll work on getting the info for the other questions.

[Makeitdo22]

I was able to blow through the vent tube and plug it with my finger while blowing. It seems like it is one continuous tube.

I ran the engine this afternoon and here is the SDS data when idling warm:
Engine Speed: 656 rpm
Ignition Timing: TDC
Manifold Absolute Pressure: 9.07 inHg (30.7 kPa)
Barometric Pressure: 30.12 inHg (101.9 kPa)
Cylinder Temp: 144 F
Intake Air Temp: 81 F
Battery Voltage: 14.28 V
Fuel Injector Pulse Width: 3264 us
Injected Fuel Amount: 13 mcc
High Fuel Pump Duty: 44.8%
IAC Valve Duty: 30%
Ex-Mani Temp STBD: 138 F
Ex-Mani Temp PORT: 141 F
Throttle Position Angle: 0
Throttle Position SNSR Output: 0.70V

When cold, the intake air temp was 70 F and the Manifold Absolute Pressure was 9.50 inHg.

I don't have a way to pull the voltages directly off the sensors. If the above SDS data is insufficient, is there an easy way to find the sensor voltages without buying a troubleshooting harness?

[redlowrey]

Check the positive crank case ventilation system, all the hoses pvc valve, when the engine over heated it may have collapsed a hose and check the cowl for blockage in the air intake.

The air that goes through the throttle assembly, crank case, then out via the pcv valve, inlet manifold is calculated with injection pulse width, if the system is blocked there will be too much fuel and not enough air even though the computer is delivering the right amount of fuel.

To have soot on the mid section every time you go out tells me that there’s not enough air in the combustion chamber for the amount of fuel being delivered.
The engine can run rich from obvious problems, you have checked all that, the sds information looks alright your engine is going to run a bit richer at the moment because of the fuel in the crank case, for it to make the plugs look a bit wet would take a lot of fuel mixed with the oil.

Just for my curiosity can you check the temp sensor voltage key on when the engine is hot, I don’t think there is any thing wrong, the sds is taking the analog voltage and converting it to a digital signal.
And with the vent hose suck and blow with it connected.

[Moonlighter]

Just to add to Red’s comment about checking the cowl for blockage in the air intake tract, definitely do that! We had another member here some time ago with similar issues and it turned out that some small bird had made a nest inside the cowl intake tract, he had to pull it apart to clean it out!! Once done, problem solved!

[Makeitdo22]

I like the logic. I had not thought about checking for an airway obstruction. I don't think I've ever desired to find a nest inside my cowl as much as today! Unfortunately/fortunately, I found no obstructions in the cowl baffles or the air intake before air enters the throttle bodies. I didn't see any obstructions further downstream into the cylinders when I had the intake system disassembled during the fuel injector cleaning. I checked the two PCV hoses (breather hoses per the schematic) that exit the top of the cylinder heads and connect back to the air intake and they are clear. There is no physical pressure control valve on this engine. I cannot find it on the schematic either. I do not see signs of excessive heat that would deform any rubber or plastic. The SDS does not provide the voltage for the temp sensor (or I cannot find it). It did give me the throttle position sensor voltage and angle - 0.7V and 0 degrees when fully closed which is spec. So that give a little confidence that the ECU is converting the voltages correctly. Confirmed that the VST vent tube is a single tube, with a single point a (VST) and point b (atmosphere). I can suck fuel vapors through it (dinner will taste funny tonight). Blowing into the tube and the VST is more difficult since the volume is contained.

I ran resistance checks on the following while it was around 70 degrees outside and they are all within spec.
Cylinder temp sensor: 2.17 kohms
STB exhaust temp sensor: 2.14 kohms
PORT exhaust temp sensor: 2.19 kohms
Inlet Air Temp sensor: 2.1 kohms (warmed up in my hand while measuring)
Vacuum Switching Valve: 41.4 ohms
Crankshaft position sensor 207 ohms

I was really hoping to find a bird nest!

[redlowrey]

Going on what you were saying that three plugs appeared wet, and there is soot on the mid section has to be not enough air. If it was because of the fuel in the oil you would think it would effect all cyls.

You have checked and made sure that both throttle plates open the same amount, that would restrict air to three cylinders, if one of the plates wasn’t opening all the way, but I am not sure if they crisscross.

As far as fuel getting into the crankcase past the rings I have a theory on that, and most of the engines run perfect, pull the plugs and they are white, telling you that all the fuel in the combustion chamber is being burned.

Your plugs are terrible, indicating a bad problem, if it was my engine I would run thicker oil, you are in a hot part of the country and no variable valve timing, because running the engine with the oil so diluted runs the risk of doing a big end bearing.

What does the oil pressure drop to at idle when it is hot.

[Makeitdo22]

Double checked the throttle plates today. They are perfectly linked. I'm not sure how to read the exact oil pressure. I did not see it as an option on the SDS display. I'll be happy to check if I now where to find it. I measured the oil pressure sensor with the voltmeter and it shows 0V when the engine is off and 5V with it running which appears to be spec for that sensor. Regarding the thicker oil viscosity, the manual confirms that this engine use take 20W-50 with temps as low as 14 degree F. The coldest I've ever seen here is 18F, and my Florida blood is too thin for operating in that! For background, this engine has "made oil" with both the Suzuki and AMSOIL 10W-40 marine oils.

I agree that the A/F ratio seems to be off somehow. Since there are no air obstructions and the fuel system is all sat, along with sat sensors that impact the A/F, I'm leaning to trying to perform the O2 Feedback procedure. My limitations to perform it are 1) I don't know where the sensor goes not the engine and 2) I don't have the proper wiring harness that has plugs for the O2 sensor, the ECU, and a USB for the computer. Any help with these items would be very helpful. The manual calls for performing this every 200 hours. Given the price of fuel, I'd like to squeeze out all the efficiency that this thing can give!

But before jumping to the O2 Feedback, I am tracking one last thing: ECU voltage through the infamous white wire (WW). I found today that the WW coming out of the ECU box goes directly to the 15 amp in-line fuse and then terminates on the same bolt as the battery cable. I've already ordered cable to re-run this to the battery (or BlueSea Battery selector switch). What I found odd is that I do not see where the WW connects into the wire harness coming from the console. The wiring schematic shows this, yet I do not see a three way connection between the WW going to the battery, WW going to the ECU, and WW going to the console. Any help understanding where this junction needs to be will be very helpful (or maybe it is inside the ECU box and I just need to look harder). I'd like to rig it properly once I know what "right" looks like. Perhaps the solution to the problem will be as simple as having a properly rigged WW?

Thanks for helping me get this far.

[redlowrey]

Gee did I go down a rabbit hole, I was looking at the picture of the plugs on my phone, they looked a lot worse, when I got home I then went to the computer screen, the top three look a bit ordinary dark tan color, I cant tell from the shot of the bottom three. If a plug was wet, the cyl would not be firing, before the plug would get to the stage of not firing the porcelain would turn black then go to soot, the spark would track then the injector would be firing into a dead cyl.

Can you check the temp sensor voltage with your multimeter easy to do when you start up cold the voltage should be over two volts and drop below one volt at operating temp, also did you check the map sensor signal voltage with the map sensor removed connected up, key on with a hand held vacuum pump and checked that the voltage corresponds to the manifold vacuum in your manual.
I don't see the soot I thought I could see when I was looking at the pictures on my phone.

[redlowrey]

Can you also check and see how much timing advance you have at 2,500rpm.